This invention relates to a magnetron device, and more particularly to improvements on means for suppressing electromagnetic waves emitted from the filament terminal of the magnetron device which act as noises to other electronic devices such as a television sets or radio sets.
It is generally known that a magnetron device emits noises having frequencies ranging approximately between 100 KHz and 1,000 MHz from the filament terminal, thus harmfully affecting other electronic devices such as a television sets or radio sets. With the prior art magnetron device, part of the filament circuit for applying voltage to a filament was generally shared by part of the anode circuit for applying voltage across the filament and anode in order to simplify the circuit arrangement. Accordingly, applying of voltages to the magnetron body containing the filament and anode could be effected through two filament terminals provided on the shield box and two power supply lines connected to said corresponding filament terminal. A magnetron device is generally provided with a filter device connected to each of two power supply lines and comprised of a choking element and capacitor to reduce or suppress such noises; and a shield box for receiving the filter devices and filament terminal. Various improvements have hitherto been made on the filter device of a magnetron. Some improvements are already set forth in U.S. Pat. No. 3,697,804. This known filter device can effectively reduce or suppress the noise induced from a magnetron through filament terminals, whose frequency has a relatively broad band ranging approximately between 20 MHz and 1,000 MHz. However, the prior art filter devices failed effectively to reduce or suppress noise having lower frequency bands than described above, for example, frequency bands of the order of several to 30 MHz. The reason is that since relatively large current such as 10 to 15 amperes flows through the filament of a magnetron device, difficulties have been presented in increasing the inductance of the choking element of a filter device connected to the filament from the standpoint of designing a magnetron device.